The present invention relates to a bogie frame for a magnetically levitated vehicle or a railway vehicle for traveling on rails. The term "bogie" is herein used to designate a wheeled carriage which is also called a "truck".
Rolling stock bogie frames known heretofore have been fabricated principally of steel materials. The weight of the bogie frame accounts for a large proportion of the total weight of the bogie. As an effort to minimize the weight, a number of measures for reducing the weight have been proposed. Among such proposals are those relating to the use of aluminum alloys and fiber-reinforced plastic (FRP) materials for the bogie frames.
More specifically, FRP material containing carbon fibers or glass fibers for reinforcement are used to fabricate long structural members, which are generally of tubular shape with rectangular cross section in the bogie construction of the type mentioned above. Hollows of the structural members are filled with foamed urethane. Thus core members are made. A plurality of the core members are assembled and wrapped with an FRP cover member to form main beams of the bogie frame. By this construction the bonding area between the core members and the covering FRP cover material is increased. As a result increased are tensile and shear strengths of the bogie frames. At the same time, the weight of the bogie frame is reduced. Such a construction is disclosed in Japanese Patent Appln. Laid-Open Publn. No. 62 264,935.
In another proposal for a rolling-stock bogie frame, FRP materials are used and a plurality of hollows are formed by means of spaced parallel webs fixed within each of elongated tubular members of rectangular cross section. Each hollow is filled with a filling material comprising fiber strands and foamed urethane. An object of the construction is reduction of the weight of the bogie frame. The above proposal is disclosed in Japanese Patent Appln. Laid-Open Publn. No. 62-244,755.
In a rolling-stock bogie frame of still another proposal, beam members are fabricated from elongated tubular members of rectangular cross section made of a carbon-fiber reinforced plastic material and filled with a filling material. By this construction, reduction in weight is sought. The construction is disclosed in Japanese Patent Appln. Laid-Open Publn. No. 61-143,257.
In each of the proposed bogie frames described above, each main beam member comprises an elongated tubular member of rectangular cross section made of an FRP material, and a filling material inserted into the tubular member. The construction of the known proposal aims at reduction in weight by using relatively thin outer sheathing in comparison with the case of bogie frames with hollows without the filling material. For this reason, the proportion of the filling material relative to the total weight becomes large. Moreover, the interiors of the bogie frame beams cannot be utilized for such purposes as accommodating an air tank or an air pipe for the pneumatic shock absorbing system.